The Behavior of a Fluorenyl-Based Host Compound in Four Organic Alkylnitrile Solvents

The host behavior of the compound 4,4′-(9-fluorenylidene)diphenol (H) bearing two rigid fluorenyl moieties and two alcohol functional groups was investigated in the presence of four alkylnitriles, namely acetonitrile (ACE), acrylonitrile (ACRY), propionitrile (PROP), and butyronitrile (BUT). Crystal growth of H from each of these nitriles furnished 1:1 host:guest inclusion complexes in each instance. Computational methods were employed in order to compare the low energy conformations of H with the guest-free molecular structure in the crystal obtained from single crystal X-ray diffraction analysis. Each of the complexes crystallized in the monoclinic crystal system and the centrosymmetric space group P21/n, and the host packing was isostructural in each case. The nitrile guest compounds experienced a classical (host)O–H···N(guest) hydrogen bond with the host molecule, the H···N, O···N, and ∠DHA parameters being 1.97, 2.772(3) Å, 159° (H·ACE), 1.94, 2.759(2) Å, 166° (H·ACRY), 1.91, 2.738(3) Å, 167° (H·PROP), and 1.95, 2.779(2) Å, 171° (H·BUT); this bond was thus significantly shorter in the PROP-containing inclusion compound than in the remaining three clathrates. The thermal stabilities of the four complexes were also examined together with Hirshfeld surface considerations. Finally, lattice energy calculations were carried out and the results of these compared with the relative thermal stabilities of the four complexes.